Recently, the liquid crystal display has spread in quick tempo and at the same time has come to be used also in the fields requiring an excellent design such as the fields of game machines, watches and portable telephones. In these fields there is a gradually increasing demand for the colorization of a polarizer, but a colored polarizer capable of satisfying a required design is not available yet at present.
The polarizer generally adopted widely in liquid crystal displays utilizes a linear dichroism obtained by impregnating a plastic material such as a polyvinyl alcohol with iodine or a colorant and by subsequent stretching or the like, thereby allowing the iodine molecules or the colorant molecules to be oriented in a certain direction (see "How to use Cptical Parts and Points to be Noted," Optonics. Co., page 51, ISBN4-900474-03-7). In such a polarizer, a component of an incident light which component is parallel to the orienting direction of the molecules is absorbed. In colorization, therefore, a colorant molecule is needed which absorbs only the light of a desired zone selectively. Besides, a colorant molecule is required to exhibit a highly efficient linear dichroism and a high stability under high temperature and humidity. Thus, there arises the problem that the number of utilizable colorants is limited. In the manufacturing process, moreover, a process for the impregnation of colorant molecules is needed, thus giving rise to the problem that the impregnation process becomes complicated in order to produce different colors.
As one of methods for obtaining a colored polarizer in an optical manner without using such a colorant as mentioned above, there is known a method which utilizes the circular polarization selectivity of a cholesteric liquid crystal.
The cholesteric liquid crystal has a property of reflecting only the light of a specific wavelength selectively, and a colored polarizer which utilizes this property has also been proposed (see, for example, JP1-133003A).
However, the ordinary cholesteric liquid crystal involves the problem that it possesses the property of specular reflection and that therefore it is inferior in visibility. The method which utilizes a cholesteric liquid crystal is advantageous in that the color purity of reflected light is high, but involves a basic problem such that the mass production of a uniform cholesteric liquid crystal free of any defect or orientation disorder is difficult. Thus, it cannot be said that the method in question is a simple method.